1. Field of the Invention
The invention relates to a connector for mounting an integrated circuit on a circuit board or a connector for connecting a circuit board to another circuit board, and a method for manufacturing such a connector.
2. Description of the Related Art
A ball grid alley type (hereafter referred to as BGA type) connector is conventionally used as a means for mounting an integrated circuit or a circuit board on another circuit board. This BGA type connector comprises a case formed of an insulating material and placed on the circuit board, a through-hole penetrating the case vertically, and a terminal electrically connecting a pin attached to the through-hole to an electrical circuit of the circuit board via a solder ball acting as a thermally fusible conductive material. This solder ball is attached to a concave portion located at a position where the through-hole faces the circuit board. The solder ball is attached in a manner it is partially welded at a lower end of the terminal. The electrical circuit of the circuit board is connected to the terminal by placing the connector on the circuit board with the solder ball mounted and by heating these members to melt the solder ball.
The solder ball between the circuit board and the terminal used by such BGA type connector of the prior art as mentioned above sometimes has a problem that the solder ball comes off the concave portion of the case before being attached to the circuit board, resulting in incomplete connection. It is difficult to manufacture a solder ball having no deformation in a process of once melting solder to form it spherically. The solder ball may be deformed before being attached to the connector because of its low hardness. Therefore, it is difficult to secure coplanarity that shows degree of how uniformly the height of the lower end of each solder ball is horizontally aligned when the solder ball is used to connect the circuit board to the terminal. Thus, there arise places where some solder balls are in contact with the circuit board while the other solder balls are not when the case with the solder balls attached to is placed on the circuit board. This may cause incomplete connection between the terminal and the electrical circuit when the solder balls are melted.
A manufacturing cost of the solder balls themselves becomes high because they must be formed precisely. As it is necessary to surely arrange the solder ball on the concave portion provided in the case and to securely fix it on the terminal, there are problems that manufacturing processes become complicated, and the total cost of manufacturing connectors becomes high.
An object of the invention is to improve a connector, more specifically to provide a connector which can be easily manufactured and can be connected to a circuit board in good condition in order to solve the problems.
In order to achieve the object, a connector according to a first embodiment of the invention is one to be surface-mounted on a circuit board having an electrical circuit and used to attachably connect an integrated circuit or another connector provided with a plurality of pins extending downward to the circuit board having the following features:
Firstly the connector comprises a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin, a connecting section facing the electrical circuit and a body section joining the contact section and the connecting section, and a thermally fusible conductive material existing between the connecting section and the electrical circuit. The connecting section extends substantially in parallel with the circuit board and comprises an internal passage connecting upper and lower sides of the connecting section, and the thermally fusible conductive material is attached to the upper and lower sides of the connecting section through the internal passage.
As the thermally fusible conductive material is vertically arranged on the connecting section through the internal passage, the connector according to the first embodiment of the invention can freely move between the upper and lower sides of the connecting section through the internal passage when the thermally fusible conductive material is heated and melted. When the connector is surface-mounted on the circuit board, the thermally fusible conductive material is heated in a condition of being in contact with the electrical circuit. When a space formed between the connecting section and the electrical circuit is filled with the heated and melted thermally fusible conductive material, an excessive amount thereof between the connecting section and the electrical circuit moves upward through the internal passage. Therefore, short circuit to the thermally fusible conductive material of an adjacent terminal and to the electrical circuit can be prevented because no thermally fusible conductive material extends in the right and left direction.
On the other hand, when the connectors are surface-mounted on the circuit board, the thermally fusible conductive material is heated and melted in the condition the thermally fusible conductive material is in contact with the electrical circuit, and when the space formed between the connecting section and the electrical circuit is not filled with the thermally fusible conductive material located in the lower side of the connecting section, the thermally fusible conductive material existing in the upper side of the connecting section moves to the lower side of the connecting section through the internal passage to fill the space between the connecting section and the electrical circuit. Thus the connecting section and the electrical circuit are surely connected.
As mentioned above, according to the first embodiment, even when a clearance between the connecting section and the electrical circuit varies, or even when an amount of the thermally fusible conductive material located at the lower side of the connecting section varies, vertical movement of the heated and melted thermally fusible conductive material enables an appropriate amount of the thermally fusible conductive material to always fill the space between the connecting section and the electrical circuit. Therefore, it is possible to prevent the short circuit to the thermally fusible conductive material of the adjacent terminal or to the electrical circuit or lack of the amount of the thermally fusible conductive material between the connecting section and the electrical circuit.
In the connector according to the first embodiment, it is possible to form the connecting section into a pair of bar-shaped pieces extending and branching substantially in parallel with the electrical circuit, and to form the internal passage by allowing the tip ends of the pair of bar-shaped pieces to be close to each other to provide an annular or a C-letter-like shape. In addition, it is possible to form the connecting section into a plate substantially in parallel with the circuit board, and to form the internal passage into a connecting hole connecting the upper and lower sides of the connecting section. The internal passage can be also formed through the connecting section by providing the connecting section with such shape.
In the connector according to the first embodiment, it is preferable that a surface of the body section comprises a groove or a step. When the surface of the body section is provided with the groove or the step like this, the heated and melted thermally fusible conductive material is prevented from moving upward along the surface of the body section because the groove or the step blocks a way of the thermally fusible conductive material going to move upward. Thus, a sufficient amount of the thermally fusible conductive material filling the space between the connecting section and the electrical circuit can be secured.
It is possible to coat the surface of the body section close to the connecting section with a substance having low wettability of solder. One of the substances having low wettability of solder is, for example, metal plating such as nickel plating. As coating of the surface of the body section with the substance having the low wettability of solder can prevent the heated and melted thermally fusible conductive material from moving upward over a position coated with the substance, a sufficient amount of the thermally fusible conductive material filling the space between the connecting section and the electrical circuit can be secured.
A connector according to a second embodiment of the invention is one to be surface-mounted on a circuit board having electrical circuit and to attachably connect an integrated circuit or another connector provided with a plurality of pins extending downward to the circuit board having the following features:
Firstly the connector comprises a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit, and a thermally fusible conductive material existing between the connecting section and the electrical circuit. The connecting section comprises a pair of bar-shaped pieces branching and extending substantially in parallel with the circuit board, and the thermally fusible conductive material is held between the pair of bar-shaped pieces and fixed by caulking. Holding the thermally fusible conductive material between the pair of bar-shaped pieces and caulking like this enables the thermally fusible conductive material to be fixed on the connecting section securely.
In the connector according to the second embodiment, it is preferable that the pair of bar-like pieces comprises a pair of first claw sections protruding inward from both sides at the tip ends each other and a second claw section at the root portion, and when the thermally fusible conductive material is fixed to the pair of bar-like pieces by caulking, the first claw sections and the second claw section penetrated into the thermally fusible conductive material, enables the thermally fusible conductive material to be fixed to the connecting section more securely.
It is possible to form the connecting section into an annular shape by allowing tip ends of the pair of bar-shaped pieces to be in contact with each other, or into the one having a C-letter-like shape by allowing the tip ends of the pair of bar-shaped pieces to have specified clearance between them.
A connector according to a third embodiment of the invention is one to be surface-mounted on a circuit board having an electrical circuit and to attachably connect an integrated circuit or another circuit provided with a plurality of pins extending downward to the circuit board having the following features:
Firstly the connector comprises a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit, and a thermally fusible conductive material existing between the connecting section and the electrical circuit. The connecting section is formed to be a plate substantially in parallel with the circuit board and provided with an internal passage penetrating from one side to the other, and the thermally fusible conductive material is inserted through the internal passage and fixed. The connector according to the third embodiment can prevent the thermally fusible conductive material from coming off the terminal because the thermally fusible conductive material is inserted and fixed in the internal passage.
As for a method for fixing the thermally fusible conductive material in the internal passage, the internal passage can be formed to be a round hole, and the thermally fusible conductive material can be fixed by caulking by crushing the round hole at a side of the connecting section from one side to deform it into a heart-like shape hole as viewed horizontally. The thermally fusible conductive material can be fixed by caulking by crushing the round hole at a side of the connecting section from two sides to deform it into an 8-letter-like shape as viewed horizontally. The thermally fusible conductive material can be fixed by caulking by crushing the round hole at the sides of the connecting section from at least three sides to deform it into a nearly rectangular shape hole as viewed horizontally.
The internal passage can be formed to be a connecting hole, and the thermally fusible conductive material can be fixed by caulking by externally pressing and bending the connecting section in a diagonal direction to reduce an opening area of the connecting hole.
The internal passage can be formed to be the connecting hole, and the thermally fusible conductive material can be fixed to the connecting section by caulking by deforming to make a width larger than that of the connecting hole at the upper and lower sides of the connecting section in a condition the thermally fusible conductive material is inserted into the connecting hole. When the thermally fusible conductive material is deformed to be fixed by caulking, the shape of the thermally fusible conductive material facing the circuit board can be made uniform at a time of caulking. Therefore, the terminal and the electrical circuit can be surely connected because coplanarity of each thermally fusible conductive material protruding from the case can be improved.
The internal passage can be formed to be the connecting hole, and the thermally fusible conductive material can be fixed by being press fitted in the connecting hole. In this case, the thermally fusible conductive material can be formed to be the one slightly wider than the connecting hole or an inner wall of the connecting hole can be provided with projections protruding in the internal direction to allow the thermally fusible conductive material to be press fitted so that the projections penetrate into the thermally fusible conductive material. The internal passage can be formed to be a recess cut in from the tip end of the connecting section, and the thermally fusible conductive material can be fixed by being press fitted in the recess.
A connector according to a fourth embodiment of the invention is one to be surface-mounted on a circuit board having an electrical circuit and to attachably connect an integrated circuit or another connector provided with a plurality of pins extending downward to the circuit board having the following features:
Firstly the connector comprises a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit, and a thermally fusible conductive material existing between the connecting section and the electrical circuit. The connecting section is formed to be a plate substantially in parallel with the circuit board and provided with a pair of recesses from both sides, and the thermally fusible conductive material is formed into wire and fixed in a condition of being wound around the pair of recesses.
A connector according to a fifth embodiment of the invention is one to be surface-mounted on a circuit board having an electrical circuit and to attachably connect an integrated circuit or another connector provided with a plurality of pins extending downward to the circuit board having the following features:
Firstly the connector comprises a case made of an insulating material, a through-hole penetrating the case from one side to the other and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit, and a thermally fusible conductive material existing between the connecting section and the electrical circuit and fixed to the connecting section. The thermally fusible conductive material is provided with a projection having a wall thickness reducing toward the circuit board side.
In the connector according to the fifth embodiment of the invention, the thermally fusible conductive material is provided with a projection having a wall thickness reducing toward the circuit board side and the projection has a surface area per volume larger than spherical material like a solder ball because it has a thin wall. Therefore, when ambient temperature is raised to allow the thermally fusible conductive material to be melted, the projection is easily melted by absorbing heat. As the thermally fusible conductive material provided with the projections is melted more easily than the solder ball like this, time required for heating the circuit board and the connector is reduced, leading to an improvement of productivity of the circuit board on which the connector is surface-mounted.
The bottom surface of the case is provided with a plurality of the thermally fusible conductive materials of which tip ends have projections. Therefore, even when coplanarity of the tip end of each projection is not so good, the connecting section of the terminal and the electrical circuit can be connected in good condition because the tip end of the projection is easily melted by heating at a time of surface mounting, resulting in high coplanarity.
In the connector according to this fifth embodiment, the projection can be formed into a conical shape having a diameter reducing toward the circuit board, it can be formed into a cross shape protruding toward the circuit board, or it can be formed into a cylinder toward the circuit board and internally provided with a depression having a diameter enlarging toward the circuit board side.
In the connector according to the first through fifth embodiments, the thermally fusible conductive material can be a solder having a cylindrical body extending vertically which is filled with flux. As the flux has a property to allow the solder to be easily melted, using the solder containing the flux as the thermally fusible conductive material enables the solder to be melted in a short time when the connector is heated to be surface-mounted on the circuit board.
In the connector according to the first through fifth embodiments, the thermally fusible conductive material can be a cylindrical solder having a central hole penetrating vertically, and attached to the connecting section to connect between the upper and lower sides of the connecting section by the central hole. Cream solder is generally applied to the surface of an electrical circuit and often contains flux. Therefore, when the connector is heated to be surface-mounted on the circuit board, the solder is melted in a short time because the flux contained in the cream solder of the electrical circuit is evaporated and enters an interior of the solder through the central hole.
A method for manufacturing a connector according to the first embodiment of the invention is one for manufacturing a connector to be surface-mounted on a circuit board having an electrical circuit, to attachably connect an integrated circuit or another connector provided with a plurality of pins extending downward to the circuit board comprising a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit, and a thermally fusible conductive material existing between the connecting section and the electrical circuit and fixed to the connecting section, and having the following processes.
Firstly, there is a terminal forming process for forming a pair of bar-shaped pieces extending and branching substantially in parallel with the circuit board in forming the terminal by punching a metal sheet. Then there is a conductive material fixing process for forming after holding the thermally fusible conductive material between the pair of bar-shaped pieces by caulking, or holding the thermally fusible conductive material, which has been formed into a specified shape, between the pair of bar-shaped pieces by caulking. There is an attaching process for attaching the terminal filled with the thermally fusible conductive material to the through-hole of the case.
A method for manufacturing a connector according to the second embodiment of the invention is one for manufacturing a connector to be surface-mounted on a circuit board having an electrical circuit, to attachably connect an integrated circuit provided with a plurality of pins extending downward to the circuit board or connect the circuit board to another one, comprising a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit and fixed to the connecting section, and a thermally fusible conductive material existing between the connecting section and the electrical circuit and fixed to the connecting section, and having the following processes.
Firstly, there is a terminal forming process for forming a connecting hole penetrating from one side to the other in the connecting section when in forming the terminal by punching a metal sheet. Then there is a conductive material fixing process for inserting the thermally fusible conductive material through the connecting hole and deforming the connecting section to fix the thermally fusible conductive material by caulking, or inserting the thermally fusible conductive material through the connecting hole and deforming it at upper and lower sides of the connecting hole to fix the connecting section by caulking, or fixing the thermally fusible conductive material to the connecting section by being press fitted in the connecting hole. There is an attaching process for attaching the terminal with the thermally fusible conductive material fixed to the penetrating hole of the case.
By the methods for manufacturing the connectors according to the first and second embodiments, the thermally fusible conductive material is securely fixed to the terminal because the thermally fusible conductive material is attached to the case in a condition the thermally fusible conductive material is fixed to the terminal in the conductive material fixing process. As it is not necessary to form the solder ball as in the prior art, the thermally fusible conductive material such as wire solder can be used at low cost without using expensive solder ball. It is necessary only to attach the terminal with the thermally fusible conductive material fixed, to the case, and a complicated process wherein the solder ball is placed in a concave portion provided on a bottom surface of the case in order to be fixed to the terminal as in the prior art is not required. Thus, the cost for manufacturing the connectors can be reduced.
As for the methods for manufacturing the connectors according to the first and second embodiments, it is preferable to provide a horizontally aligning process wherein the tip ends of the thermally fusible conductive material protruding toward the circuit board side are horizontally aligned after the attaching process. As each of the thermally fusible conductive material can be made in contact with the electrical circuit in the horizontally aligning process when the connector is placed on the circuit board, the terminal can be securely connected to the electrical circuit when the thermally fusible conductive material is melted.
In the horizontally aligning process, tip ends of the thermally fusible conductive material can be horizontally aligned by allowing the tip ends of the thermally fusible conductive material protruding toward the circuit board side to be in contact with a horizontal plate and pressing them toward the horizontal plate in order to align the tip ends horizontally to deform the tip ends of the thermally fusible conductive material. In the horizontally aligning process, the tip ends of the thermally fusible conductive material protruding toward the circuit board side can be allowed to be in contact with the horizontal plate heated at a temperature close to but less than a melting point of the thermally fusible conductive material and can be horizontally aligned by deforming the tip ends of the thermally fusible conductive material by heat.
In the thermally fusible conductive material fixing process by the method for manufacturing the connectors according to the first and second embodiments, when the thermally fusible conductive material is fixed to the connecting section, a length of the thermally fusible conductive material protruding from the connecting section to the electrical circuit side can be determined corresponding to a clearance between the case and the circuit board when the case is placed on the circuit board in a condition the terminal and the thermally fusible conductive material are attached.
In the prior art, the clearance (standoff) between the case and the circuit board is adjusted by changing a diameter of a solder ball, however changing a diameter of the solder ball leads to an increase of cost such as equipment investment because it is necessary to modify equipment for positioning the solder balls at the time of welding the solder balls on the terminal. By the method for manufacturing the connectors according to the first and second embodiments, the standoff can be easily adjusted by changing a position where the thermally fusible conductive material is held by the connecting section in the thermally fusible conductive material fixing process or by changing the length of the thermally fusible conductive material. Therefore, the standoff can be easily adjusted corresponding to a variety of standards without causing a great cost increase as in the prior art.
A method for manufacturing a connector according to the third embodiment of the invention is a method for manufacturing a connector to be surface-mounted on a circuit board having an electrical circuit, to attachably connect an integrated circuit provided with a plurality of pins extending downward to the circuit board or connect the circuit board to another one, comprising a case made of an insulating material, a through-hole penetrating the case vertically and into which the pin is inserted, a terminal having a contact section provided in the through-hole to be in contact with the pin and a connecting section facing the electrical circuit and fixed to the connecting section, and a thermally fusible conductive material existing between the connecting section and the electrical circuit and fixed to the connecting section, and having the following processes.
Firstly, there is a terminal forming process wherein a connecting hole or a recess penetrating from one side to the other of the connecting section in forming the terminal by punching a metal sheet. Then, there is an attaching process for attaching the terminal to the penetrating hole of the case. There is a conductive material forming process for forming a projection having a wall thickness reducing toward the electrical circuit side and forming an inserting section having a diameter smaller than that of the connecting hole or the recess of the connecting section in the terminal side. There is a conductive material fixing process for arranging the thermally fusible conductive material according to the position of the terminal, inserting the inserting section into the connecting hole or the recess, and caulking the inserting section from the upper side of the connecting section to be deformed so as to have a diameter larger than that of the connecting hole or the recess in order to fix the thermally fusible conductive material to the connecting section of the terminal by caulking.
By the method for manufacturing a connector according to the third embodiment, the thermally fusible conductive material can be prevented from coming off the terminal because the inserting section is inserted into the connecting hole or the recess provided at the connecting section of the terminal to fix the thermally fusible conductive material by caulking.